Today, virtually all grades of paper, cardboard and the like are produced from aqueous pulp slurry. Typically, the pulp is suspended in water, mixed with various additives and then passed to equipment in which the paper, cardboard etc. is formed, pressed and dried. Irrespective of whether mechanically produced pulp, semi-chemically produced pulp, unbleached chemical pulp or pulp made from recycled fibres (i.e. pulp prepared from recycled paper, rags and the like) is employed, it is often necessary to add various strengthening agents to the pulp in order to obtain an end product having adequate strength properties. In the case of paper and board for use in packaging and the like, the tensile strength and tear strength under dry and wet conditions are of primary importance; moreover, notably in the case of certain grades of cardboard (e.g. so-called unbleached board for the manufacture of corrugated cardboard boxes for packaging, transport and the like), the compression strength of the material is often also an important factor.
Among the strengthening agents used today there are a number of environmentally undesirable substances which it would be desirable to replace by more environmentally acceptable materials. As examples hereof may be mentioned epichlorohydrin, urea-formaldehyde and melamine-formaldehyde.
The industry is also looking for environmental friendly methods for increasing the strength and/or the shape-retention and/or the anti-wrinkling properties of cotton textiles. Today various cross-linking technologies are in use:
DMU technology, in which dimethyl urea and a catalyst are used; this technology has the disadvantage that formaldehyde is released; PA0 DMDHEU technology, in which dimethylol dihydroxyethylene urea and a catalyst are used; this technology has the disadvantage that some formaldehyde is released+the cellulosic material becomes stiff; PA0 BTCA technology, in which butane tetracarboxylic acid and a catalyst are used; this technology has the disadvantage that the formed ester has low durability+the process is expensive.
Thus there is a need in the industry to find a more environmental friendly process for improving the strength and/or shape-retention and/or anti-wrinkling properties of various cellulosic materials; said process should preferably at the same time give a product with a high durability.